The present invention relates generally to infrared detectors and more specifically the invention pertains to a Schottky diode infrared detector with a voltage tunable cutoff wavelength.
Infrared detectors are used to convert photons whose energy is in the IR portion of the electromagnetic spectrum to electrons. Once converted, these electrons are removed from the structure and external circuits are used to convert the information obtained into signals that may be viewed on a standard television monitor. This reconstruction allows for an invisible IR image to be presented in a manner that can be understood by an observer.
The infrared spectrum is considered to extend from just above the visible band (0.4 to 0.7 .mu.m) out to more than 30 .mu.m. Detectors can be fabricated from many materials that will respond to photons in the 1 to 30 .mu.m spectrum. They are usually characterized by having a spectral response that is defined by the electronic band structure of the material. The structure allows for infrared detection to occur over a specific band of wavelengths. If a new wavelength band is desired, then a new material must be manufactured. There are no materials that are easily tunable by external means during operation after having been fabricated.
The task of providing a voltage tunable Schottky diode infrared detector is alleviated, to some extent, by the systems disclosed in the following U.S. Patents, the disclosures of which are incorporated herein by reference:
U.S. Pat. No. 4,533,933 issued to Pellegrini et al;
U.S. Pat. No. 6,319,204 issued to Wong, and
U.S. Pat. No. 5,107,317 issued to Takasaki.
The patent to Takasaki discloses the use of a Ge-containing crystalling layer as an intervening layer between an GaAs layer and a compound semiconductor layer. The Wong patent is of similar interest.
While the above-cited references are instructive, none of the cited patents disclose a Schottky diode infrared detector with a voltage tunable cutoff wavelength which is obtained by inserting a SiGe layer between the metal suicide and the Si substrate.